1. Field of the Invention
Telecommunication and, more specifically, a video teleconferencing system that allows conferees to converse naturally.
2. Introduction
For decades individuals have attempted to make teleconferencing into a technology that can replace the telephone as the primary technology for communicating from remote locations. The names "teleconferencing," "video teleconferencing," "video-conferencing," and "video-phone" all refer to both audio and visual communication from separate locales and all are the subject of this invention. Soon, with the completion of the nationwide digital infrastructure, it will be possible to transfer large amounts of live high-resolution video signals inexpensively. It is foreseeable that teleconferencing may become the preferred technology of choice for communicating from separate locations and that video-phone teleconferencing may become as significant a communication breakthrough as the telephone itself.
Although matters of signal compatibility and "information superhighways" may greatly influence the ultimate success of teleconferencing, apparently simple matters such as the placement of the camera may be even more important. The arrangement of mounting a video camera on the outside perimeter of a television monitor remains today the most common layout for a system of teleconferencing. This teleconferencing arrangement, however, has significant drawbacks that limit its successful use in providing natural conversation. First, when a conferee looks at the image of the other conferee on the monitor he/she attempts to make eye contact as in a normal conversation. Unless the video camera is directly behind the image on the screen, the conferee will fail to look into the video camera. At the same instance, the other conferee will do exactly the same thing and will also fail to look directly into the video camera. In such a situation the conferees can see one another but do not achieve eye contact. This is known as a parallax problem and is a significant deterrent to having natural conversation. Human beings are conditioned to expect eye contact. When someone avoids eye contact, one unconsciously assumes they are lying or perhaps hostile. Thus, a failure to make eye contact can be fatal to teleconferencing.
When the video camera is mounted above the monitor, to the conferee viewing the transmitted image the other conferee appears to be looking in a downward direction. Likewise, when the video camera is mounted at the bottom of the monitor, the imaged conferee seems to look upward, and when the camera is mounted to the left or to the right of the monitor, the imaged conferee appears to be gazing to the right or the left, respectively. Another drawback to the perimeter-mounted video camera has been the difficulty of correctly framing a person's image. When a conferee moves from left to right or up and down or back and forth, his image leaves the frame and/or is off-center or is too small or too large. This framing problem is distracting and affects the quality of conversation. To avoid this problem the conferees must not move while conversing. This enforced stillness can be uncomfortable and prevents natural conversation because most people often move and shift their body positions.
3. Related Art
The parallax problem is not unique to teleconferencing. It is a common problem in television broadcasting where an announcer must be able to look straight into a television camera and yet still be able to read a printed script. Consequently, some of the prior art comes from the broadcasting industry. Various prompting systems comprising transparent mirrors or polarizing screens have been perfected to cause the text to seem to float in front of the announcer so he can read the material and look at the camera at the same time.
A number of similar systems comprised of polarizers and transparent mirrors have been developed for teleconferencing. U.S. Pat. No. 5,117,285 to Nelson et al. mounts a single-angled mirror and a camera to the front of a monitor. The camera is aimed at the critical angle at the transparent mirror so that it views a reflected image of the conferee. Meanwhile, the conferee is able to look through the transparent mirror to see the monitor and the image of the second conferee. U.S. Pat. No. 4,928,301 to Smoot uses a transilluminated liquid crystal screen and a rear projection system to achieve eye contact. The screen alternates rapidly from a transparent mode in which a rear-mounted camera can capture the local conferee and a translucent mode in which the image of the remote conferee is rear-projected on the screen. U.S. Pat. No. 4,400,725 to Tanigaki teaches the use of a Braun tube as an image screen that alternates between an image display mode and a transparent mode in which a rear-mounted camera views the conferee. Still another system is taught by U.S. Pat. No. 5,159,445 to Gitlin et al., where a video camera is mounted behind the viewing side a flat panel display screen which can switch from image-producing mode to a transparent mode.
These technologies represent the prior art for creating eye contact, and each has significant limitations. These devices are often bulky, and require a specially designed, expensive monitor other than the type normally used for television or computers. In addition, they are often awkward, having variously angled polarizers and mirrors and a camera protruding from the image screen. Lastly, all of these technologies fail to allow natural conversation where conferees can move freely and yet remain centered in the image frame.
An automatic tracking device that pans, tilts, and zooms a video camera has been successfully demonstrated in the prior art. This device consists of a platform that mechanically pans and tilts. It tracks the person being shot by means of a homing device placed on the person or contained in a hand-held microphone. It is designed primarily for speakers that are giving presentations and, thus, are moving about in a room. The significant drawbacks to this system are its having a limited life due to it being mechanical and its cumbersome size when placed atop a monitor for teleconferencing. The pan, tilt, and zoom requirements for the great majority of teleconferencing needs are more subtle than the previous devices'design requirements due to the conferee remaining in a limited area in order to view the other conferee's image on the monitor.
The prior art has also produced methods of simulating panning and framing without mechanically moving the camera or lens. The medical arts have developed electronic endoscopes for imaging internal body organs at a number of magnifications. U.S. Pat. No. 4,894,715 to Uchikubo et al. teaches such an endoscope with an electronic "zooming" function. U.S. Pat. No. 4,9996,592 to Yoshida teaches a video apparatus that is capable of changing the apparent field of view of a video frame by electronically selecting a portion of a digitized image and committing the selected portion to an electronic memory. However, this device does not store the entire image for remote selection and manipulation.